Hard disk drives are common information storage devices. FIG. 1a provides an illustration of a typical disk drive unit 100 essentially consisting of a series of rotatable disks 101 mounted on a spindle motor 102, and a Head Stack Assembly (HSA) 130 which is rotatable about an actuator arm axis 105 for accessing data tracks on disks during seeking. The HSA 130 includes at least one drive arm 104 a head gimbal assembly (HGA) 150. Typically, a spindling voice-coil motor (VCM) is provided for controlling the motion of the drive arm 104.
Referring to FIG. 1b, the HGA 150 includes a slider 103 having a HAMR head (not shown), and a suspension 190 to load or suspend the slider 103 thereon. The suspension 190 includes a load beam 106, a base plate 108, a hinge 107 and a flexure 109, all of which are assembled together. A write transducer and a read transducer (not shown) are embedded in the pole tip of the slider 103 for writing and reading data. When the disk drive is on, a spindle motor 102 will rotate the disk 101 at a high speed, and the slider 103 will fly above the disk 101 due to the air pressure drawn by the rotated disk 101. The slider 103 moves across the surface of the disk 101 in the radius direction under the control of the VCM. With a different track, the slider 103 can read data from or write data to the disk 101.
This HAMR head is an improve magnetic head which applies a thermal energy source (a semiconductor light source generally), such as a laser diode at or near the location of the write transducer. This thermal energy source provides heat energy or light energy to the recording medium, which reduces the medium's coercivity to facilitate the writing process. Concretely, as the coercivity is reduced, thus the magnetization directions of the recording medium are changed by the magnetic field of the magnetic head, so that the data can be recorded. The HAMR head can use smaller magnetic particle, and larger magnetic anisotropy can be obtain at room temperature, so as to ensure a sufficient heat stability required when recording on an increased surface density. Therefore, this HAMR head becomes more and more desirable.
Commonly, it's necessary for the semiconductor light source to perform several testing before it is used in the magnetic head, such as burn-in testing which is needed to apply heat energy thereon. Conventionally, the burn-in testing is carried out in chip level, that is, the semiconductor light source bar is cut into separated semiconductor light source chip firstly, and then the semiconductor light source chips will be tested one by one. However, the testing efficiency is quite low, which is not desired by manufacturers. In view of this drawback, an efficient testing method was developed. The burn-in testing is performed in bar level, namely the burn-in testing is carried out on the semiconductor light source bar directly before cut into separated chips, which can improve efficiency significantly. However, a new issue of temperature uniformity is generated. Due to local heat will be generated and accumulated in the semiconductor light source bar during burn-in testing, which causes temperature uneven across the semiconductor light source bar and the heat could not be dissipated properly. As the local temperature of the semiconductor light source bar, such as the laser diode bar increases, on one hand, the conversion efficiency of electrical input to optical output falls so that, for a fixed electrical input, laser output declines. On the other hand, as the local temperature of the laser diode increases, the temperature required in the burn-in testing can not be achieved, which affects the testing result or damages the laser diode bar and, in turns affects the performance of the HAMR head.
Thus, there is a need for an improved system and method for cooling the semiconductor light source bar during burn-in testing that do not suffer from the above-mentioned drawbacks.